In the multimedia field, various types of digital data streams need to be transmitted jointly in some form, in which case they need to be processed appropriately for transmission.
In the following text, the expression digital data streams should in no way be regarded as relating exclusively to types of digital data which are normally processed in data packets of a size which can be predetermined, that is to say with a number of bytes which can be predetermined:                digital data, with which text is written, for example a text file,        audio data,        video data.        
The document N. Färber et al., “Extension of ITU-T Recommendation H.223 for Error-Resilient Video Transmission”, IEEE Communication Magazine, page 120–128, June 1998 (“Färber et al.”) discloses a method and a system for processing a digital data stream in accordance with ITU-T Standard H.324.
The ITU-H.324 Standard is likewise disclosed in Färber et al.
FIG. 4 illustrates symbolically the design of a system for transmitting a digital data stream, as is known from Färber et al., and this will be explained briefly in the following text.
FIG. 4 shows what are referred to as application layers 401, 402 and 403. One possible configuration of the application layers is described in ITU-T Draft Recommendation H.223, International Telecommunication Union, Telecommunication Standardization Sector, August 1996 (“ITU-T reference”). For the purposes of transmission of a digital data stream, the application layers 401, 402 and 403 should be regarded only symbolically as something using which a data stream, normally in data packets of a size which can be predetermined, is in each case supplied to an adaptation layer, which will be described in the following text.
The general principle is that different application layers supply different data streams, for example a video data stream VD, an audio data stream AD or a text data stream, to the appropriate adaptation layer.
FIG. 4 shows the application layer 401 which supplies the text data stream TD to the adaptation layer 411, the application layer 402 which supplies the audio data stream AD to the adaptation layer 412, and the application layer 403 which supplies the video data stream VD to the adaptation layer 413.
An adaptation layer should be regarded as something using which an error identification and/or error correction measure can be carried out.
An error identification and/or error correction measure should be regarded, in the following text, as a method using which it is possible to identify and/or to correct any errors in the transmission of a data stream.
Various principles for error identification and/or error correction are likewise known from Färber et al., for example what are referred to as repeat request methods (Automatic Repeat Request Methods, ARQ Type I, ARQ Type II), or else what are referred to as methods for forward error correction. In the context of methods for forward error correction, a distinction is drawn between error-identifying methods and error-correcting methods.
The data streams VDT, VAD and VVD with error treatment applied to them in the respective adaptation layers 411, 412 and 413 are supplied to a multiplexing layer 420. The multiplexing layer 420 should be regarded as a layer at which the supplied data streams VDT, VAD and WD are grouped to form an entire data stream, GDS.
A V 34N.8 modem 430 is used to process the entire data stream further such that the processed entire data stream can be transmitted in a network 440.
A video compression method is known from ITU Draft 21 of the Recommendation H.263, Version 2, Transmission of Non-Telephone Signals: Video-Coding for Low Bit Rate Communication, Feb. 1998 (“ITU Draft 21 reference”).
A method for processing an entire data stream having data packets in a first data stream and data packets in a second data stream is known from WO 98/21846, in which the data packets each have an error identification field, and in which the entire data stream is received by a first layer.
The known systems and methods have, in particular, the disadvantage that it is impossible to associate associated data packets from different data streams, which data streams have been transmitted, with one another without a fundamental change to the transmission method.